Impedimetric detection of histamine in bowel fluids using synthetic receptors with pH-optimized binding characteristics.

Histamine is a biogenic amine that is indispensable in the efficient functioning of various physiological systems. In previous work, a molecularly imprinted polymer (MIP) based sensor platform with impedimetric read-out was presented which could rapidly and at low cost determine histamine concentrations in buffer solutions within pH 7-9. For diagnostic applications, histamine should be detectable in a wider pH range as it mostly occurs in mildly acidic environments. To understand this pH-dependent response of the MIP sensor, we propose a statistical binding analysis model. Within this model, we predict the theoretical performance of MIP based on acrylic acid in the required pH range and verify these results experimentally by UV-vis spectroscopy, microgravimetry, and impedance spectroscopy. Using impedimetric read-out, specific and selective detection of histamine in the physiologically relevant nanomolar concentration range is possible in neutral and mildly acidic phosphate buffer. Finally, this sensor platform was used to analyze the histamine concentration of mildly acidic bowel fluid samples of several test persons. We show that this sensor provides reliable data in the relevant concentration regime, which was validated independently by enzyme-linked immuno sorbent assay (ELISA) tests.

Biomimetic Bacterial Identification Platform Based on Thermal Wave Transport Analysis (TWTA) through Surface-Imprinted Polymers.

This paper introduces a novel bacterial identification assay based on thermal wave analysis through surface-imprinted polymers (SIPs). Aluminum chips are coated with SIPs, serving as synthetic cell receptors that have been combined previously with the heat-transfer method (HTM) for the selective detection of bacteria. In this work, the concept of bacterial identification is extended toward the detection of nine different bacterial species. In addition, a novel sensing approach, thermal wave transport analysis (TWTA), is introduced, which analyzes the propagation of a thermal wave through a functional interface. The results presented here demonstrate that bacterial rebinding to the SIP layer resulted in a measurable phase shift in the propagated wave, which is most pronounced at a frequency of 0.03 Hz. In this way, the sensor is able to selectively distinguish between the different bacterial species used in this study. Furthermore, a dose-response curve was constructed to determine a limit of detection of 1 × 104 CFU mL-1, indicating that TWTA is advantageous over HTM in terms of sensitivity and response time. Additionally, the limit of selectivity of the sensor was tested in a mixed bacterial solution, containing the target species in the presence of a 99-fold excess of competitor species. Finally, a first application for the sensor in terms of infection diagnosis is presented, revealing that the platform is able to detect bacteria in clinically relevant concentrations as low as 3 × 104 CFU mL-1 in spiked urine samples.